Water Quality

By Graham Quick © 2007

A note to the clear water people; while clear water is a bonus it does not follow that because the water is clear it is OK. Think about the following...

Customer says: 'my water is clear so it must be OK'
my answer: 'Sulphuric acid is clear but would you put your fish in it?'

Oxygen, while I bang on about it and getting a test kit I still have to tell people every day why the sturgeon die and other fish live. They do not tolerate levels as low as other fish will. Please buy an oxygen test kit and use it! You cannot look at a pond and say how high the oxygen level is hence test kits were made!

Once open liquid test kits generally only produce accurate results for 6 months. After this it may not be possible to rely on them so use them, don't waste them. Keep a record so you know what is happening. This shows trends starting such as declining hardness, which can lead to a pH crash.

pH Crashes

Recently a number of people have been reporting pH problems.

A Few facts:

• pH is based on a logarithmic scale i.e. 7.0 is 10 times less acid than 6.0
• The hardness (that buffers the pH) is naturally 'used' by bacteria in the natural process of nitrification.
• Acid rain; unless you have rainwater running in to your pond this should not have much effect.
• A stable pH is better than a variable one even if it is at the limit tolerated by the fish.
• To help reduce downwards pH fluctuations use crushed oyster shell in the filter. This can be purchased from Feed Merchants normally £6-£10 for 25kg (it is the same product sold by koi dealers for 10 x the price).
• Never change more than 1 pH point per day unless absolutely necessary.
• Ammonia is not toxic if the pH is below 7.0
• A low pH (less than 7.0) also reduces the nitrification process.
• Salt (sodium chloride) does not increase the pH.

Ideal Pond Levels for sturgeon

• pH 6.5 - 8.0
• Total Hardness (CaCO3) 50-400 ppm
• Oxygen (02) > 6mg per litre
• Ammonium (NH3) < 0.01 mg/litre
• Nitrite (NO2) < 0.1 mg/litre
• Nitrate (NO3) < 100 mg/litre
• Optimum temperature range 4ºC to 25ºC
• Optimum growth 22ºC

The most important are Oxygen, Ammonium and Nitrite. But check all of them!

Pond Volumes

How to work out your pond volume:

• The easiest way is to measure the volume with a water meter when you fill the pond.
• For square/ rectangular ponds it is easy length x width x depth = m3 if measured in metres or ft3 if in imperial.
• For round ponds diameter x depth x 3.142 = m3 or ft3.
• For irregular ponds average width x average length x average depth = m3 or ft3

Once you have the volume you can work out the number of gallons or litres.

Some basic information:

• There are 6 1/4 gallons in a cubic ft i.e. 1 ft3
• There are 1000 litres or 220 gallons in a cubic metre i.e. 1m3 = 1000 litres = 220 gallons

A pond example:

In feet:
My pond is 28 ft x 14ft x 4 1/2ft deep = 1764 cubic ft

So Number of gallons 1764 x 6 1/4 =11025 gallons.

In metres:
8.60 x 4.30 x 1.38 = 51.03 m3

= 51030 litres or 51.03 x 220 (gallons per m3) = 11023 gallons

There is a small difference in the volumes due to the fact that I have rounded the figures off to the nearest whole number.

If you can't do it don't guess, ask a friend to work it out for you.